1. Field of the Invention
The present invention relates to an organic electroluminescent device, and more particularly to a red-light organic electroluminescent device and an organic electroluminescent compound applied thereto.
2. Description of the Related Art
Because of low weight and high efficiency, flat panel displays, such as liquid crystal displays, have been widely developed. However, liquid crystal displays have some problems, such as viewing angle, response speed, driving power and color. More particularly, liquid crystal displays cannot be fabricated with large size.
To date, organic electroluminescent displays have gradually overcome the size issue and above-mentioned problems
The organic electroluminescent devices perform display by using organic electroluminescent material. The device includes two electrodes and an organic electroluminescent layer between the electrodes. When a current or voltage is applied to the device, holes from the anode will recombine with electrons form the cathode within the organic electroluminescent layer and generate excitons. When the excitons release energy and are back to the ground state, a portion of energy generated therefrom will transfer into photons.
In Applied Physics Letters, Vol. 51, No. 12, pp 913-915 (1987), C. W. Tang and S. A. VanSlyke disclosed a double-layer organic electroluminescent device, which includes a pair of electrodes, an organic electroluminescent layer and a hole or electron transporting layer. When electrons and holes are injected by the electrodes and go through the electron or hole transporting layer, they recombine within the organic electroluminescent layer and generate photons. The colors of light generated from the device depend on the electroluminescent material.
In Japanese Journal of Applied Physics, Vol. 27, No. 2, pp L269-L271(1988) and Journal of Applied Physics, Vol65, No. 9, pp. 3610-3616 (1989), a triple-layer organic electroluminescent device is disclosed, which includes a pair of electrodes, an organic electroluminescent layer, a hole transporting layer and an electron transporting layer. Moreover, it also showed that low driving voltage and high brightness are feasible.
For full-color display, purity of colors is very essential. The advantage of organic electroluminescent material is that the wavelengths of the lights can be tuned by modifying the structure of the compounds thereof.
However, some issues of the organic electroluminescent device should be overcome, especially in stability and efficiency of the organic electroluminescent device. Traditionally, tris(8-quinolinol) aluminum (AlQ3) doped with DCM or its derivatives are used as the red-light organic electroluminescent layer. The material still cannot provide organic electroluminescent device with high brightness and good color purity.